AQA A Level Physics

• 7 Base SI Units

  • Moles
  • Kelvin
  • Seconds
  • Metres
  • Kilograms
  • Amperes
  • Candela
• work out watts in Base SI Units

  Kg m^2 s^-3
• What is under the graph in a velocity-time graph? Displacement
• Newton's Laws


  • An object will remain at a constant velocity unless acted upon by a resultant force
  • Resultant force is directly proportional to the rate of change of momentum
  • If object A exerts a force on object B, then object B will exert a force of equal magnitude and opposite direction, of the same type of force on object A
• Law of Conservation of momentum:

  The Total momentum before a collision is equal to the total momentum after a collision in a closed system.
• Current


  The rate of flow of charge
• Ohm's Law


  Potential difference across a circuit is directly proportional to the current, provided all physical conditions and temperatures remain the same
• Types of Dispersion


  • Material dispersion - different wavelengths of light travel at different speeds in the same medium
  • Modal Dispersion - light waves spread so light travelling along the same optical fibre might take longer paths to reach the end. This is called multipath dispersion(can result in pulse broadening)
• LDR


  As light intensity decreases, there are fewer free electrons available to conduct. This leads to a lower current. As the current has reduced and R= V/I, the resistance of the LDR decreases
• Quark composition of a neutron:

  Up

  Down

  Down
• Quark composition of an antineutron: Antiup, antidown, antidown
• Young Modulus


  To work out the young modulus from a stress-strain graph, you must take the gradient of the graph at the start when it is still directly proportional
• Longitudinal wave


  A wave where the vibrations are parallel to the direction of energy transfer
• Coherent waves


  Waves that have the same frequency and same phase difference
• Factors affecting speed of a stationary wave on a string

  • Tension in the string
  • Mass per unit length of the string
• Kaon


  Meson particle that contains strange quarks
• Plane polarisation


  Vibrations are in one plane only, which indicates the direction of wave travel
• de Broglie wavelength


  Used when treating particles such as electrons or neutrons as a wave
• Photon energy


  The type of energy used in the equation E=hf
• To convert eV into J, just multiply by 1.60 x 10-19
• Ionisation energy


  Energy required to completely remove an electron from an atom
• Conditions for total internal reflection


  • Travelling towards a boundary from a more optically dense substance
  • Angle of incidence needs to be greater than the critical angle
• Elastic collision


  Kinetic energy is conserved
• Forces responsible for centripetal acceleration

  • Gravitational
  • Electromagnetic
  • Friction
  • Magnetic
  • Normal Reaction
  • Lift
• Electric field


  A region of space within which a charged particle experiences a force
• Magnetic flux density


  Measured in Teslas
• Magnetic flux


  Measured in Webbers
• Magnetic flux linkage


  Measured in Webbers
• Producing a current in a wire moved between the poles of a horseshoe magnet at right angles


  1. Wire experiences a change in magnetic flux

  2. This induces an e.m.f in the wire

  3. If part of a complete circuit, the e.m.f causes there to be a current in the wire
• Resonance


  When the forcing frequency matches the natural frequency of a system, causing it to vibrate with a greater amplitude (causing the maximum rate of energy transfer)
• A 230 Volt Alternating current supply is used in the mains electricity at home.

  
  

  If 230 V is the root mean squared voltage, then the peak value will be 230 x root 2= 325V
• What needs to be conserved according to particle conservation laws

  • Charge
  • Baryon number
  • Lepton number
  • Strangeness
  • Energy
  • Momentum
• What else has to be conserved when particles interact, other than Baryon Number, Leptop Number, Strangeness and charge

  • Energy(Law of conservation of Energy)
  • Momentum (law of conservation of Momentum
• Constituents of


  • Baryon: Three quarks
  • Meson: One quark and one anti quark
• During a particle interaction, the strangeness can change by 1 when it is a weak interaction, as weak interactions do not necessarily conserve strangeness
• Internal energy


  The random distribution of the potential and kinetic energy of the molecules in a substance
• The kinetic energy of a gas is dependant upon the temperature of the gas
• Couple


  A moment caused by a pair of equal magnitude forces acting in opposite directions through a different line of action
• Conditions required for nuclear fusion

  • Extremely high temperatures/pressure
  • To overcome electrostatic repulsion between nuclei
  • Extremely high density
  • To ensure the rate of collisions between nuclei is high enough
• Conditions required for Simple Harmonic motion


  • Acceleration is directly proportional to the displacement from equilibrium position
  • Acceleration is in the opposite direction to displacement/ directed towards the equilibrium position